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Unformatted text preview: hernandez (ejh742) homework 13 Turner (58120) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A car with mass 665 kg passes over a bump in a road that follows the arc of a circle of radius 37 . 4 m as shown in the figure. The acceleration of gravity is 9 . 8 m / s 2 . 3 7 . 4 m v 665 kg What is the maximum speed the car can have as it passes the highest point of the bump before losing contact with the road? Correct answer: 19 . 1 m / s. Explanation: At the highest point, we have mg- N = mv 2 r , where N is the normal force. To get the maximum speed, we need N = 0 . Therefore, v max = g r = radicalBig (9 . 8 m / s 2 ) (37 . 4 m) = 19 . 1 m / s . 002 (part 1 of 2) 10.0 points A small sphere of mass m is connected to the end of a cord of length r and rotates in a vertical circle about a fixed point O. The tension force exerted by the cord on the sphere is denoted by T . r O What is the correct equation for the forces in the radial direction when the cord makes an angle with the vertical? 1. T- mg sin =- mv 2 r 2. T- mg sin = + mv 2 r cos 3. None of these 4. T- mg cos = + mv 2 r correct 5. T + mg cos = + mv 2 r 6. T- mg sin = + mv 2 r 7. T- mg sin =- mv 2 r tan 8. T- mg sin = + mv 2 r tan 9. T + mg sin = + mv 2 r Explanation: O mg T The centripetal force is F c = mv 2 r . This centripetal force is provided by the ten- sion force and the radial component of the weight. In this case, they are in opposite hernandez (ejh742) homework 13 Turner (58120) 2 direction, so F c = mv 2 r = T- mg cos . 003 (part 2 of 2) 10.0 points What is the magnitude of the total accel- eration? You may want to first find both the radial and the tangential component of the acceleration. 1. | vectora | = radicalBigg parenleftbigg T m parenrightbigg 2- 2 g cos T m + g 2 cor- rect 2. | vectora | = radicalBigg parenleftbigg T m parenrightbigg 2 + g 2 3. | vectora | = radicalBigg parenleftbigg T m parenrightbigg 2 + 2 g cos T m + g 2 4. | vectora | = radicalBigg parenleftbigg T m parenrightbigg 2 sin 2 + g 2 cos 2 5. | vectora | = radicalBigg parenleftbigg...
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